Method of adding glass colorant composition

ABSTRACT

COLORANT-ENRICHED FRIT GLASS COMPOSITIONS OF THE FOLLOWING INGREDIENTS ARE DISCLOSED TOGETHER WITH METHODS OF PRODUCING COLORED GLASSES USING SAME:   PERCENT BY WEIGHT   COMPOSI- COMPOSI- COMPOSITION 3 TION 1 TION 2   INGREDIENTS: SIO2 15-50 CR2O3 2-10 2-10 R2O 23-26 NA2O X 21-30 10-40 K2O (1) 0-7 B2O3 10.5-47 49-70 35-70 R2O PLUS B2O3 44-74 FE2O3 0-10 COO 0-8 0-43 MNO 0-18 0-23 PBO,BAO AND ZNO 0-15 NIO 0-18 FE2O3 0-18 AS LEAST 2%. CUO 0-28   1 LESS THAN 25% X.

May 14, 1974 E, C. HAGEDORN FTM y METHOD 0F ADDING GLASS COLORANT COMPOSITION Filed May 8. 1972 l/// v QN Q j e f7 QM nited States Patent' Oce ser. No. 251,421

Im. cl. Cosb /16 U.S. Cl. 65-134 .l Y

,9 Claims p l y ABSTRACT OF THE DISCLOSURE f Colorantienriched fritglass compositions of the followingl ingredients are disclosed together with methods of producing colored glassesusing same:

i Percent by weight Composl- Composi- Composltlon3 v tionl 1 tion2 A Ingredients:

CROSS-,REFERENCE To RELATED APPLrCA'rIoNs i' The present y'application is a continuation-impart of applicationSer. No. 21,375, led Mar. 20, 1970 and vnow abandoned, which is a division of application Ser. No. 579,971,1iledSeptj16, 1966,`no'w U.S. Pat. No. 3,561,- 985 issued Feb. 9, 1971, which in turn is av continuationin-part of applicants formerly copending application Ser. No. 285,088,'filed June 3, 1963, and now abandoned. .This invention relates to a colorant-enriched glass suitableY for vuse'in""t:' loring a base glass and, more par# ticularly, to a colorant-enriched glass frit having a high concentration of chromium,v o xides. l. A

` Colo'rantenriched 'glasses suitable for forehearth addition', in frit or molten form, to a" colorless base glass to forma composite color glass arel known, as are colorantenriched glass 'frits containing chromium oxides. A number'bf patents disclosing such frits for making colored glasses and ultraviolet absorbent glasses, the latter having aspeciiic concentration of chromium oxide wherein .the chromium is hexavalent, have been issued to the assignee of the present application. I

Descri tion of theV prior art 1 l Colorant-enriched glass compositions are disclosed in Hagedorn U.S. Pat. No. 3,024,121 granted Mar. 6, 1962;

3,810,745 Patented May 1 4, 1974 t t 2 Swain U.S. Pat. No. 2,923,636 granted Feb. 2, 1960; and Babcock U.S. Pat. No. 3,024,120 granted Mar. 6, 1962. In general, however, such frits as disclosed in these patents haveV high melting temperatures and/or relatively high viscosities when molten, so as to present certain ditiiculties and disadvantages in the processessfor forming colored glasses. These include higher costs due to the need of increased Vtemperatures to melt the frit, volatilization and consequent loss of certain of the ingredients in the glass because of the high temperature, increased tendency for the chromium and other colorant oxides at high percentages to crystalli'ze and form inclusions in the resulting colored glass, and diiculty in thoroughly dispersing the molten frit throughout the molten base glass due to the relatively high viscosity of the molten frit. Solution and devitriiication problems are greatly increased, especially in the production of highly reduced chromium frits.

lSUMMARY OF THE INVENTION `Accordingly, it is an object of the present invention to I provide a colorant-enriched glass composition suitable for use in coloring a base glass, and which is free of the aforementioned difficulties and disadvantages.

It is a further object of the present invention to provide a family of colorant-enriched glasses suitable for use in coloring a base glass, which glasses have low melting temperatures, low viscosities, and are readily miscible with colorless molten base glasses to form uniformly colored glasses.

It is another object of the present invention to provide Vglasses having a high concentration of chromium oxides, Vi.e., from about 2 to about 10% or more, and which, when addedtin frit or molten form to a colorless molten base glass, impart a yellow-green, green, or blue color to the base glasses, and which, if desired, will also impart the ability to absorb substantially all ultraviolet radiation to whichl it may be subjected.

In attaining the objects of the present invention, one

Vfeature resides in maintaining the silica content of the colorant-enriched glass at a low level While maintaining a highrconcentration of a mixture of alkali metal oxides and B203 wherein the total of the alkali metal oxides and B203 is from 44% to 74% by weight of the colorantenriched glass, which glass has a lower viscosity and is more readily miscible with the molten base glass than conventional high-silica-coloring frits.

Another feature of the invention resides in forming a colorant-enriched, silica-free glass having a critical content of alkali metal oxides and B203, which glass can be formed at a temperature as low as from about 1200"- l400 F., and which has a low viscosity relative to known highly colorant-enriched glass frits, so that it can readily be added to and mixed with a molten base glass at the forehearth to' produce a uniform color in the resulting glass article.

Other objects, features, and advantages of this invention will become more apparent from a reading of the following disclosure.

DESCRIPTION OF THE PREFERRED Y EMBODIMENTS Glass frits having the capacity to dissolve significant amounts of various colorant oxides such as chromium, co-

- 0-7 49--70 Over 2 A0--10 Percentby-vveigth FegOa t 'l When the amounts of K2O, Na2O, and B203-were outside ofthe `ranges set forthabove, attempts. tommake the colorant-enriched glasses or 'frits'were unsuccessful duc to the formation. of chromium oxide. crystals in the glasses.

It has also been found that high colorant-enriched 65A glasses usefuly for forehfearth'a'dditin to a *moltenI base glass can be made without lthe vpre'sence'of any silicaand such glasses, useful'for addition as fritsl or byfdirectaddition to the forehearthhn molten form, haveA thefollowing essential ingredients: 'l

70' Ingredients:-

to about 10 percent by weight of the -glassefrit .composi- 75,

25% by weight of the former. The foregoing compositions 60 can accommodate, ywithout recrystallization, more than 2% by weight of the various colorant oxides. Thurs, the compositions of the invention contain more V than 2% chromium oxides in the vitreous state.

When colorant-enriched glass frits made in accordance., withthisinvention are to be stored for any length of time prior to use, it has been found that `the presence of .A1203 in the frit composition increases the chemical durability of the frit while simultaneously preventing the agglomeration of the frit particles. When forehearthfrit additionsV are made, it is important that the frit particles be freeowing and readily dispersble throughout the molten base glass. The presence of a suicient amount of alumina, up

The total amount of CrzOa in the vitreous state in the Usually these frits are within the composition range: composition will vary from aboye 2 A,toabout V,10% or.V j f more. Minor amounts of the following oxides may also-if- OXldvi: u vPefellt byweight be present without materially affecting the low melting.l B203 35-70 temperature or relatively low viscosity of the above-com- Y Niko 1040 position. N10 `018 Percent byweight l Total Iron as Pesos 0-18 C00 '0.3" 'Total' manganese as MnO 0 23 MnO 0-18 I 08 0 43 Illustrative examples of silica-free, highly colorant- 10 u 0 28 enriched glasses coming within the scope of the invention (wherein the combined colorant oxide content is at least are set forth in the following table: 2% by weight).

TABLE IIL-COLORANT-ENRICHED GLASSES y A y l Percent by weight (M) (N) (0) (P) (Q) (R) (Si).y 4 (T).,`(U)

2.16 4.16 447" 4.75 4.90 6.2 4.98 422v 4126* 65.4 49.35 53.0 56.35 58.17 58.0 59.12 55.87 56.11 3.5 6.73 7.23 7.68 7.93 10.0 8.06 ggg 6.88 7.76 Mno 17.90 11.78 6.26 3.23 1.64 Again, it is to be understood that the maximum amounts It is usually preferred that at least 5% of the particular of these added oxides are not to be present at one time. colorant oxide be present in the frit to minimize the If one wanted, one could add up to about 10% or more amount offrit to be added to achieve the desired degree of SiO2 to the aforesaid listed compositions as long as the 30 coloration in the composite glass. ability ofthe particular composition to accommodate the In one embodiment of the present invention a single desired amount of chromium oxide in the vitreous state colorant oxide from the above list is present in the yalkali was not materially affected, borate frit. The amount of colorants will be at least '2% In practicing the present invention, it is often advanby Weight and preferably 5% by weight of the frit comtageous to adjust the density of the frit glass to approach position. The maximum amount of colorant will be .that the density of the base glass inthe interest of eficiency shown in the above table.

in mixing. We have found that this can be accomplished., For instance, in the sodium borate system containing a by incorporating the oxides of lead, barium, zinc, and single colorant oxide, the composition ranges are as fol'.h

mixtures thereof into the sodium borate frit composition. lows:

For.inst anc e, ordinary soda-,lime base glass has a density 40 Qf}abou t.2.5 gm-fcc., whileqcertain of the sodium borate vf V Pereemz' fritsfoffthe invention haye a density f aboutf2.4 gni/cc. l v Broad Preferred nlhasbeieaf m1 rha'uilie densityofthefrircan be'ifi'- eutanasia@ compnet..-

...n-g, lt'pred` to ach ye optimummixmgby rncorporatingup to Nikelasthelsmglexl v t f colorant N Ov Iron as the sing colorant.

Manganese as the single' 'I N'.

ngle

.l ',111 fthe fsbsc .et the xides' or chromium.' the alkali borate system of the invention is an excellent'vehiclefor the forehearthI addition of other colorant metal oxides to a molten base' glass: ,We havffound-that-"these alkali '20.0 t borate glasses,`particularly the sodium borate glasses, are

capable of dissblving'unexpected amounts Vof the oxides v v l 't of nickel, iron, manganese, cobalt, copperland mixtures 70 im 150 ''""""""-*-5j thereof. It" will be understood thatthe rn 1ximum solu- D'eugnl'lm bility of Iany particular colorant 'oxidev occurs when all t. p y other colorants are absent, even though significant amounts The above frits were made by melting the following of the above-mentioned oxides caribe dissolved together rawbateh. materials, cooling themelt and quenching on a in a single'ffrit composition. v v '15 st'eelplate.

TABLE 1v' Parts by weight Composition (L) (M) (P) Raw materials: Sando 100.0 100.0 loo. 0

19. a5 17. 7e 1e. o 16. o

Sodium silicate (anhyd.) Lead oxide (PbaOi). MnOz Parts by weight Composition (V) (W) (X) (Y) Raw materials:

Sand

(Z) (AA) (BB) (CC) (DD) (EE) Soda ash Borax (dehyd.) Iron ehrnmitn Potassium dichromate. Cobalt oxide (C0304) Borlc acid (anhyd.) Calcium carbonate Nephellne syenlte Sodium silicate (anhyd.)

Lead oxide (PbaOi) M1104 When attempts were made to form silica-free, colorantenriched glass compositions containing chromium wherein the amounts of Na2O and B203 were outside of the ranges set forth in Tables III or II'I(a)` or III(b), chromium oxide crystals were formed in the glasses,which crystals` were extremely diicult to melt, even when the glasses were subjected to higher temperatures. Due to such crystal formations, these glasses were unsuitable for use as colorant additives to molten base glass compositions. The base composition of the silica-free frits may be Na2B4O7 which, in hydrate form (Na2B4O7-5H2O) is 'common borax. These' frits can`be melted at very low temperatures, i.e., 12001300 F. when potassium dichromate is used as the source of chromium. Such silicafree frits also have surprisingly good chemical durability. Some have shown no signs of weathering or caking over a period of a year or two and, since they are non-hygroscopic, they always feel dry to the touch.

Since the solubility of hexavalent chromium exceeds the solubility of trivalent chromium, making such frits suitable for use in producing colored ultraviolet-absorbing glasses, it has been possible to incorporate reducing agents, such as sea coal, sucrose, iron scale, aluminum metal, into the composition so as to increase the amount of Cr203 at the expense of Cr03. The total chromium oxide in the compositions set forth in the tables and the claims is expressed as .Cr203. All of the chromium oxide in the frit may be in the trivalent form (Cr203) or a mixture of the trivalent with the hexavalent form (CrO3). The actual Cr03 content of any given fr it is dependent upon two factors, namely (1) the addition of the chromium to the frit batch as dichromate and (2)the oxidation state of the frit batchduring melting. In certain examples, e.g., Examples H, I, and K, ,all of the chromium was adedas dichromate. i

In other examples, the chromium was added as equal parts by weight of potassium dichromate and chromite, a

mineral containing FeOCr2O3. In the manufacture of ultraviolet-absorbent composite glasses, a residual hexavalent chromium content is desired, and an oxidizing agent such as niter is preferably added to maintain strongly oxidizing conditions in the frit batch. A full discussion of the Cr2O3CrO3 relation is to be found in Pat. No. 2,923,636 assigned to thel assignee of the present invention.

The above colorant-enriched compositions in Examples A-U, inclusive, were prepared by melting the batch ingredients at various temperatures of from 1300-2500 E. for a time of from 1/2 to 1 hour. The batches in Examples V through FF were melted at 1600 F. for 11/2 hours'.l Platinum crucibles were used in all instances, and an air atmosphere was maintained in the furnace.

In forming a frit having a chromium content in a highly oxidized state, alkali dichromate is preferably utilized as the source of chromium. When the chromium is added as an iron chromite or a mixture containing iron chromite, all of the iron must be completely oxidized before there can be any hexavalent chromiumin the glass composition. -Frits which arerelatively high in hexavalent chromium (Cr03) are suitable for the forehearth production of ultraviolet-absorbing glasses, such as yellow-green, green, and blue glasses.

Examples H and T from the above tables, which are illustrative of highly oxidized chromium frits, were added to the following molten base glass composition. I

The resulting ultraviolet-absorbing glasses had the following compositions:

10 then added by forehearth addition to a glass having the following composition;

Weight percent 1 5 Ingredients:v Percent by weight Glass 1 Glass 2 Sio2 7212 with Frt H Frlt T A1203 1 74 VCaO 11.29

' ni AMgt?)v 1.15 10 v -Naa t 13.34 1.02 1.14

ia K2O 0.32 0.30 141 R293 Y, 0'04 0.04 .04

v `1)2 "f'bg' o :002 '.00 15 The final colored glass had the following composition: C.I.E. data (2mm.thlc ess) Percent brightness......... 82.8 36.05 z Percent purity 21. 3 9 D, minant wave length in mllllml- 567 82 o s .l v s r Pgigelintirninsminance at 400 mii (2 9 7 19 5 Prcentby weicht ci... i..F::::::::::::::::::::: To ma. 20 y it Glsgggg maggy?, 1 Yellow-green: Ingredients:

S i-.. 70.91A 70.10 Typical base compositions which have been used foi- 15:32 lzgg forehearth frit additions of the present invention are' 25 1.12 1.12 essentially conventional glasses formed in a conventional 1(3): ig 1&2; manner, including sodalir`ne-silica glasses. The condii i 0.88 1.59 tions and procedures for making such molten base glasses ggg 3,533@ gzgg are known to those skilled in the art, as exemplified in analyzed constituents: Table IX, B-ll, on page 245 of Handbook of Glass 30 gg'aotalifonh ofbg Manufacture by Tooley, Ogden Publishing Co., New Clrigguommy 0.220 Y0S1k ,tI` I).1Y., 9533 1 l t h 'gercen brigltnes's ui a e so aime-si ica gass" `composi ions ave e Y ercen pun y following ranges of ingredients in percent by weight: Dominant wvelengthi mmmicmnLm 5555 5560 Ingredients: I Percent byweight 315- S102 60-75- typical emerald green glass has 35.0% brightness, A1203 03'10 66.0% purity, and a dominant wave length-mu of 555 .0. Cao '35f13 Fromthe graph in the drawing, the similarity in wave Mg() 0 7 40 length between a natural emerald green glass and glasses .-CaO'i'MgO '2'-v "6-15 of the foregoing examples made with Frits U and K will Naao 2"'18 be readily evident. g2g --vg- -Examplesy and W in Table ('I!lI(a) demonstrate how a the density of the frits. of the invention may vary with .i :Ua cf 45 composition. Examples X through AA demonstrate how ungvnlllllilg tsielccltsasrgw vthe density of the colorant frit I nay be adjusted to approxiing'an alkali dichromateas thesourcepof chroniilimiand mate fth'dengyothe solda'lmedbse glass through the ot o o 'n, an 'u adding thereto a Suclent amountfof Fedlligfaemsuch li-Sxeniparfu its BzllB cthraigli FF aaiemsodiuin borate acrgnestggaz) Stcalrotvlegxguga; 50 colorant f rit compositions, containing colorants other than chromiumthat are suitable for coloring soda-lime silica trivalent chromium. Combinations of sea .coal and .iron scale in the frit batch have produced highfchrome frits which, lwhen added to molten iiint4 glasses, produce .an emerald green glass comparable to the' acc'epted st 'andard emerald green. i f 'i Two frits having the chromium content in the state are shown in the followingexamples FRIT GLASS COMPOSITION The batch ingredients were melted at a-ltemperature of 2000 F. for 1 hour, cooled andfritted. The frits were base glasses-,.lhese frits are low melting and arereadily mixed with the base glass at forehearth temperatures to produceunifornily colored composite glasses,

5 5 The use of frits BB through FF is demonstrated by the following examples.

--A11 ordinary colorless soda-lime base glass of the composition: Y

wasmelted in an ordinary glas melting furnace according to the mhod described in col. 9, lines 26-31. Frit composition BB, Table fllI(b), was added to the base glass at -forehearth temperatures in the ratio of 6.7 pounds per ton of base glass. This addition was accomplished after thebase. glass had issued from the melting tank into the .715 forehearth at temperatures in the range of 2300-2600 F.

' vFrit composition DDv in'Table-'Hltb was added Vatthe rate. of 25.3' pounds of frit per ton of base glass to the colorless soda-lime Ibase glass described in col. 10, lines 6-7-5- by the forehearth method described. above..The.re sulting composite glass was light orange in color and'v had the following composition and properties: 1

Frit glass composition FF in Table III(b.)v was added to the colorless base glass described beginning' in col.' 10, lines 56-75 by the method described above'.-Th'e ratio of addition was 32.5 pounds of frit per t0n of -base glass. The resulting composite glass was blue green in color and had the following composition and properties:

While a low-silica-containing, colorant-enriched glass composition, useful in frit or molten form to l:color a molten base glass has been given above, a preferred'composition is as follows: Y l

Ingredients: i n weight.-I

Si02 L 1S- 41 Cl'03 R20 31-46 B203 21-'37 Total of R and B203 ly 52-74 R20 has the same values as given above, -andtheo'tullier oxides, also discussed abovetwith thel disclosure ofthe broad composition, may be present in the .same designated amounts.

12 I Fromtheabove disclosure, colored glasses meeting the desired optical properties and standards, as recognized Y bLtheindustrxtand .as setiorth. .in v.Hagedorn .aU-S... Pat- Si02 Percent? 72-08 L No.w.;3024,l21 and incorporated herein by reference, can A1202 dill-'i174' 5 readily"be' made' using the apparatus and methods dis- CaO Vd0` 11-05 "closed-in thel aforesaid patent. Other suitable apparatus MgO d0v-'` 0-91 and"me'thods`a`re describedin U.S. Pat. No. V3,057,175 to n Na20 'dQ-fA- 13-41 R. R. Rough. v K2O d-" 0-44 l We claim: B203 Yd0''' 0-29 10 1. 'Ihe method of producing a colored glass which com- `Fe203 d0``' 0-03 prises melting a soda-lime-silica base glass; adding to the NiO dO-- 0-05 :l molten base glass, as essentially the sole colorant, a high C-LE- data (2 mmhCkDeSS) colorant-enriched glass composition consisting essentially Percent brightness 74 .'of the following ingredients in the indicated proportions Percent purity c 8 151125, Weightg'- v Dominant wavelength mp-- A575 Ingredients: Percent by weight Si02 15-50 Cr203 (total chromium) 2-10 the total amount ofv said R20 and B202 being from 44% to74% byweight of the glass composition, said R20 being a mixture lof Na20 and K20, said K20 being present in an' amount of less than 25% by weight of said Na20, said glass composition being in the molten state in said molten bas glass, mixing the. molten composition and molten base glass and thereby producing a colored glass of improved homogeneity.

2. The method of producing a colored glass which comprises melting a soda-lime-silica base glass, adding to the moltenvbase glass, as essentially the sole colorant, a highly colorant-enriched glass composition consisting vessentially 4ofthe following ingredients in the indicated .proportions by weight:

Ingredientsz. Percent by weight Si02 18-41 C'r202 (total chromium) 4-10 the total amount of said R20 and B202 being from 52- 74% by weight of the glass frit comopsition, said R20 a mixture o f Na20 and K20, said K20 being present in an amount of less `than 25% by weight of said Na20, said glass lcomposition being in a molten state in said molten baseglass, mixing the molten composition and molten b'ase glass-and thereby producing a colored glass of im- I*proved homogeneity. y

3." Thev method of producing a rcolored glass which '-comprises melting a soda-lime-silica glass composed of not more than 50% silica, adding to the molten base glass, asessentially the sole colorant, a highly colorant-enriched glass' composition consisting essentially of the following ingredients in the indicated Yproportions by weight:

Ingredients: v

v y 4 Percent by weight Na20"`. 21-30 Klo.. M B2O2' f 49-70 Cr202 (total chromium) 2-10 said glass composition being in the 'molten state in said moltenvbase glass, mixing the molten composition and molten base glassi and thereby producing a colored glass of improved homogeneity and substantially free of chromiumojxide crystals.

4. The-.method ofproducing a colored glass which comprises melting a soda-lime-silica base glass, adding n.,to .the'moltenbase'glasas essentially the sole colorant, a highly. colorant-'enriched glass composition consisting essentially of the following ingredients in the indicated proportions by weight:

the total amount of said R20 and B203 being from 44 to 74% by weight of the glass frit composition, said R20 being a mixture of Na20 and KzO, said KZO being present in an amount of less than 25% by weight of said NagO, said glass composition being in the molten state in said molten base glass, mixing the molten composition and molten base glass and thereby producing a colored glass of improved homogeneity.

5. The method of producing a colored glass as dened in claim 1, wherein said highly colorant-enriched glass composition is a glass frit and is added to the molten base glass in frit form and is melted therein, said molten -frit being mixed with the molten base glass to produce a colored glass of improved homogeneity.

6. The method of producing a colored glass as defined in claim 4, wherein said highly colorant-enriched glass composition is a glass frit and is added to the molten base glass in frit form and is melted therein, said molten frit being mixed with the molten base glass to produce a colored glass of improved homogeneity.

7. The method of producing a colored glass as defined in claim 3, wherein said highly enriched glass composition is added to the surface of the molten base glass in molten form and including mixing said molten composition and said molten base glass to produce a colored glass of improved homogeneity.

I8. The method of producing a colored glass which comprises melting a soda1ime-silica base glass composed of not more than silica, adding to the molten base glass, as essentially the sole colorant, a colorant-enriched frit glass composition consisting essentially of l0-40% by weight of Na20 and 35-70% by weight of boric oxide and at least one colorant oxide selected from the group consisting of the oxides of nickel, iron, manganese, cobalt and copper, and mixing said base glass and said frit glass composition to produce a uniformly colored composite glass of improved homogeneity.

9. The method of claim' 8, wherein said colarant oxide includes:

Percent NiO 0 18 Total iron as Fe203 0-18 Total manganese as MnO 0-23 C00' 0-43 CuO 0-28 wherein the total colorant oxide content is at least 2% by weight.

References Cited UNITED STATES PATENTS FRANK W. MIGA, Primary Examiner U.S. Cl. X.R. -121 UN1TED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CURRECTION PATENT NO. 3,810, 745

DATED May 14, 1974 INVENTOR(S) Hagedorn and Hall It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

C01. 7, line 73, "aded" should be --added--7 Col. 10, line 43 after "Table", delete Col. lO, line 69, "glas" should be -g'1ass; Col. 11, line 66, "CrO3" should be --Cr2O3-; C01. 12, line 45, "comopsition" should be --composition--7 Col. 12, line 46, before "a" insert -being; Col. 14, line ,Signed and Sealed this Tenth Da)l of May1977 [SEAL] Attest.'

RUTH C. MASON C. MARSHALL DANN Alifsting Offitef Cnmmissimwr ujjPatents and Trademarks 

